1. Field of the Invention
The present invention relates to the field of portable terminals and more particularly, to a method and apparatus for protocol processing in a terminal that is equipped with multiple subscriber identification cards.
2. Description of the Related Art
Regular mobile communication terminals employ a single subscriber identification card. However, advances in mobile communication technology have enabled development of various types of mobile communication terminals, such as dual-mode terminals, multi-standby terminals and multi-SIM terminals. A dual-mode terminal may use one of two subscriber identification cards according to a user selection. A multi-standby terminal may make multiple subscriber identification cards active simultaneously for calls. A multi-SIM terminal includes a radio frequency unit and a baseband chip, and holds multiple subscriber identification cards. Particularly, in the multi-SIM terminal, the single radio frequency unit is alternately shared by multiple subscriber identification cards. For example, when a dual-SIM terminal holding first and second subscriber identification cards is turned on, it may perform frequency scanning and measurement for the first subscriber identification card to register the first subscriber identification card in the base station, and perform frequency scanning and measurement for the second subscriber identification card to register the second subscriber identification card in the base station. After registering the first and second subscriber identification cards, the dual-SIM terminal may perform neighbor cell scanning and measurement. However, frequency scanning and measurement, and neighbor cell scanning and measurement cause a large amount of battery power consumption. That is, as a conventional multi-SIM terminal performs frequency scanning and measurement, and neighbor cell scanning and measurement repeatedly for individual subscriber identification cards, the multi-SIM terminal may consume a large amount of battery power.
Additionally, in a multi-SIM terminal, when the radio frequency unit is used for a call on one of the subscriber identification cards, radio communication channels related to the remaining subscriber identification cards may be released. That is, when an existing multi-SIM terminal handles a call on one of multiple subscriber identification cards, it may release radio communication channels related to the remaining subscriber identification cards. This unexpected channel release may prevent the corresponding base station from keeping track of the remaining subscriber identification cards, causing network confusion.